The present invention relates to steel cables (“steel cords”) usable for reinforcing rubber articles such as tires. It relates more particularly to the cables referred to as “layered” cables usable for reinforcing the crown reinforcement of radial tires.
Steel cables for tires, as a general rule, are formed of wires of perlitic (or ferro-perlitic) carbon steel, hereinafter referred to as “carbon steel”, the carbon content of which is generally between 0.2% and 1.2%, the diameter of these wires generally being between 0.10 and 0.50 mm (millimeters). A very high tensile strength is required of these wires, generally greater than 2000 MPa, preferably greater than 2500 MPa, which is obtained owing to the structural hardening which occurs during the phase of work-hardening of the wires. These wires are then assembled in the form of cables or strands, which requires the steels used also to have sufficient ductility in torsion to withstand the various cabling operations.
For reinforcing radial tires, most frequently so-called “layered” steel cables (“layered cords”) or “multi-layer” steel cables formed of a central core and one or more concentric layers of wires arranged around this core are used. These layered cables are preferred to the older “stranded” cables (“strand cords”) owing firstly to a lower industrial cost price, and secondly to greater compactness, which makes it possible in particular to reduce the thickness of the rubberised plies used for the manufacture of tires. Among layered cables, a distinction is made in particular, in known manner, between compact-structured cables and cables having tubular or cylindrical layers.